idle reset

[blksn955.o]

some good info on idle reset using tweecer...got it from eectuning.org.

Thanks to Randy (PThornton) for the following.

Disconnect the ISC and let the car idle. Set the throttle body screw so that the car will just barely idle. Set the TPS to ~0.99. Now datalog the car for about 30 seconds after it is fully warmed up. Average the airflow and convert it to the correct units for the throttle body airflow. Set the throttle body airflow.

Now reconnect the ISC and datalog the car at several different RPM points for at least 30 seconds. Set the idle RPM to do this. Average the numbers for RPM and airflow and set the X & Y values in the ISC nuetral airflow function. You will probably have to change the X values to match the RPM values you average from the datalog as it will not match what you set the idle to.

This step is if you have problems with stalls on pushing in the clutch on coast down. Compare the new ISC settings to the old settings and figure out what percentage increase you have. For me this was the exact same percentage for all Y values in the function. Increase the dashpot pre-postion by the same percentage.

air flow conversion factor is:
MAF * 2.2046226 / 60


isc---

Setting idle air (isc).
Datalog the isc duty cycle, should be 30%. If higher, first verify that car will idle with the isc motor disconnected. It should be adjusted mechanically to idle about 100 rpm lower than the desired idle speed.
Re-connect isc motor, check duty cycle, if still too high, set the "isc neutral air flow" values to stock, adjust the air values around the desired idle rpm to obtain 30% isc duty cycle.
If you can't datalog isc duty cycle then observe the timing at idle, it should be steady.
If the timing values are hunting at idle, then that indicates you have too much or too little idle air through the isc valve and the EEC is trying to compensate by adjusting timing to control idle. This will make idle unstable though.
If you have aftermarket cams in the car you will probably need to increase the isc air values somewhat in the idle region.
If the idle hangs you can reduce or zero out the air values in the "dashpot pre-position" function to make the idle come down faster. If you zero it out it should drop right away with the exception of hanging around 1000 rpm when off throttle and car is still moving. Once it gets below 3mph it should go to idle speed
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hope to add somemore...just a quick search on some good setup/reset stuff.

 

[VibrantRedGT]

I got this from stangtuning.com

'94-'95

Begin with a cold vehicle. The idea here is to get the car to a firm cold idle with enough air bleed capacity left in the idle circuit for IAC adjustment.

The idle stop should be set first. Back out the idle stop screw, away from the bell crank arm, until about 1/2 turn past the point where it no longer makes contact (blade fully closed). Using an 0.010" feeler guage, tighten until gauge just drags between screw and bell crank arm. Remove feeler gauge. Tighten screw exactly 1 1/2 turns. If the screw is very loose, put a drop of loc-tite or silicone on it, so it doesn't work out of adjustment.

Now remove the connector to the Idle Air Controller (IAC) just on the other side of the throttle body. Start the car and allow vehicle to warm for 2 minutes. Give a small "blip" to let it settle. If it is having a hard time staying running you may have to get an assistant until you can get to the front of the car. Now open or close the air bleed screw (CCW opens) next to the IAC until the car idles at 575 to 600 rpm. For guys with aftermarket cams and an EEC tuner, you might want to idle a bit more briskly, say 650 to 675.

Obviously, this rpm range is by what the car and driver wants...ie, no set idle speed, whatever works for YOU.

Turn off the car. Now count the number of turns clockwise to close on the idle air bleed screw. If it falls between 1/2 and 2, it's okay, now reverse it out the same number of turns. Log the number somewhere in case you need it for the future. Reconnect the IAC. You are done.

If the air bleed screw is above 2 turns, it's a good idea to tighten the idle stop screw another 1/2 turn, then repeat the idle setting. If it is below 1/2 turn, then loosen the idle stop screw by 1/4 to 1/2 a turn, and repeat the idle setting. Be sure to put another drop of silicone RTV on the stop screw if it was disturbed. Reconnect the IAC. You are done.

Another variation for the 94-95 cars is to reset the idle in the procedure listed above and get the car to idle as low as possible with idle control OFF and the IAC unplugged. (around 600-650 rpms). Then plug the IAC back in, turn off the engine and unhook the negative battery post for 20 minutes. Then hook everything back up and put the desired settings in the PMS for idle control ON. Start with the percentage around 40% in the PMS air bypass setting and work from there. Once you set the desired idle RPM in the PMS, save and start the car. After a minute or two it should be able to control the idle.

 

[blksn955.o]

the first post I made was a gen. search and it brought up a question about the TPS.

I have heard that the 94-95's have a "self adj." TPS that everytime the car is started the eec makes the startup (or something) voltage the idle/base voltage...

basicly making the setting to .99v pointless...

Anyone confirm or shoot it out of the sky...related and good info to know.

 

[VibrantRedGT]

That's a vague statement I've heard for the 12 years I've owned my car. Bottom line is you bolted on a brand new TPS to the throttle body most likely it will never read .98v. It could read 1.1v or .88v. Will the EEC try to adjust it? Of course but it not without a fight. It will surge and have a hard time. The TPS will need a base to start from and the logical way is setting it at .94v-.98v from the start.

 

[blksn955.o]

That's a vague statement I've heard for the 12 years I've owned my car. Bottom line is you bolted on a brand new TPS to the throttle body most likely it will never read .98v. It could read 1.1v or .88v. Will the EEC try to adjust it? Of course but it not without a fight. It will surge and have a hard time. The TPS will need a base to start from and the logical way is setting it at .94v-.98v from the start.

same here, just wanted to try to get a "answer" to the age old question. It is always better to check and make sure no matter what though.

 

[VibrantRedGT]

same here, just wanted to try to get a "answer" to the age old question. It is always better to check and make sure no matter what though.

That's the beauty of the R/T Tweecer you have, monitor the TPS right on the screen. I set my TPS with my Tweecer and the idle was never better.

 

[blksn955.o]

that is the beautifull thing about the R/T.

 

[final5-0]

I'll have to go on record and say I don't think the .98 or .99 tps thing is anything to be all that concerned about on our cars.

If you are seeing over 1.00, then I would be concerned.

btw, there was a great thread about 6weeks to maybe a couple of months ago that had a write up from some guy that IMHO, was the best info about this subject I had ever seen.

anyway

I have seen so many dlogs where the tps value was well below the .98 value I have lost count. Those peeps did not give me any indication that the lower tps value was a prob for them.

I just looked at the last two dlogs peeps sent me and one was .767 and the other was .861

I just went back to some old dlogs with my stock tb and that value was .926

My current tb has the value of .9602

I have never set my tps
but
Do I think it hurts anything to do so ...... Not at all

The idle strategy for the fox and our cars is really different.

I remember years ago, for the longest time, everybody said you wanted to have an isc duty cycle of around 28%. I never could get mine that low no matter what I did. The lowest I could get was around 33% and at that value, the idle was not smooth. The value always seemed to prevail after each different method I tried was around 36%.

After more 94-95 folks started to come around, the word got out ...
that isc duty cycle was not possible for the 94-95 folks.

One last thing

IIRC, pthornton is a Fox kinda guy (very knowledgeable guy IMHO) so his info on setting idle may not apply to our cars.

I'm tellin ya folks

Ya gots ta be careful with sum o dat Fox Stuff

It can lead you down a path of confusion

Grady

 

[BlackVert]

what if it is like .891? that's what mine is.

i have read that it doesn't really matter because the pcm uses the volts at startup as the initial value and everything after that is an offset from that.

but i still think that i should try to get mine at least a little closer to 1.00 if possible.

fwiw, my isc duty cycle at idle is .105, which i assume means 10.5%. i'm guessing it doesn't go any lower than that because my idle is still too high, it idles around 1000, but i am telling it to idle at 800.

i think my problem is that the blower is sucking hard enough even at idle that it is getting air through the valve cover vent and up through the pcv. i am still working on proving that theory ...